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Biomedical subjects

S Belletti

Publications and source records attributed to S Belletti.

At least 19 recordsLinked to original sources
PubMed1992

A motion correction algorithm for an image realignment programme useful for sequential radionuclide renography.

The correction of organ movements in sequential radionuclide renography was done using an iterative algorithm that, by means of a set of rectangular regions of interest (ROIs), did not require any anatomical marker or manual elaboration of frames. The realignment programme here proposed is quite independent of the spatial and temporal distribution of activity and analyses the rotational movement in a simplified but reliable way. The position of the object inside a frame is evaluated by choosing the best ROI in a set of ROIs shifted 1 pixel around the central one. Statistical tests have to be ful-filled by the algorithm in order to activate the realignment procedure. Validation of the algorithm was done for different acquisition set-ups and organ movements. Results, summarized in Table 1, show that in about 90% of the simulated experiments the algorithm is able to correct the movements of the object with a maximum error less or equal to 1 pixel limit. The usefulness of the realignment programme was demonstrated with sequential radionuclide renography as a typical clinical application. The algorithm-corrected curves of a 1-year-old patient were completely different from those obtained without a motion correction procedure. The algorithm may be applicable also to other types of scintigraphic examinations, besides functional imaging in which the realignment of frames of the dynamic sequence was an intrinsic demand.

Algorithms↗
PubMed1992

A comparison of accuracy of computer treatment planning systems in brachytherapy.

An intercomparison was made between dose-rate point calculations with five commercial computer treatment planning systems used in brachytherapy. Sixteen Italian radiotherapy medical physics institutions performed a twofold test, respectively for point and linear sources, reproducing actual clinical implants and the results were compared to references values. The test was designed in order to determine the errors introduced separately by computation and by implant reconstruction via orthogonal films. The results show that for point sources a better accuracy can be achieved than for linear sources. It is also shown that a large variation of results exists between computation systems and the variability is larger for linear sources. The digitizing procedure adds a large amount of error. In the whole set of calculation points, the overall percent difference between computed and reference dose-rate values is larger than +/- 5% in 18% cases for point and in 52% cases for linear sources, with data input by digitizer. It seems that relevant errors do occur when computing actual dose rates, resulting in clinically relevant inaccuracies in the calculated absorbed dose and in its relative effectiveness.

Algorithms↗
PubMed1992

[Results of the quality control of magnetic resonance images].

The results are reported of an image quality control performed by the Medical Physics Dept. of Spedali Civili, Brescia, Italy, after the implementation of an MR unit (Siemens-Magnetom 1.5 T) in the Radiology Department. Image quality parameters were evaluated, with the methods suggested in literature, for test objects images acquired in the conventional projections (axial, sagittal, and coronal) using RF body and head coils. Our aim was to evaluate system evolution during optimization of the equipment and to identify, when possible, eventual situations of stability and the time needed to achieve them. The results obtained for the uniformity and the signal-to-noise ratio parameters are evaluated as time curves with the analysis of linear regressions of parameters evolution over time. The measurements were made over a 14-month period, on a fortnight basis. The long-term variations are emphasized. The uniformity parameter exhibits no significant changes over time, while signal-to-noise ratio tends to increase, mostly due to noise decrease. Noise was observed to stabilize in the last months. A second analysis, with a statistical test on the difference of two subsequent measurements, was carried out to confirm this trend. Stability periods could be identified for all parameters. As for noise, in particular, a stability interval from May to October 1990 confirmed the regression results. A normality range was defined in this period as a reference for subsequent measurements.

Magnetic Resonance Imaging↗
PubMed1991

[The characteristics of a low-melting-point alloy (Lipowitz's metal) for use in radiotherapy].

Lipowitz's metal is widely employed in radiotherapy to create shielding blocks and compensators for X- and gamma-rays. Its effect in modifying radiation beams cannot be evaluated in a simple manner: therefore, in our opinion, an experimental approach to the problem is the most suitable one. Attenuation for Lipowitz's metal and lead was measured in some different geometrical setups, for a 5 MV linac and a 60Co unit. Transmitted fraction vs attenuator thickness curves were obtained. The influence of attenuators on depth-dose curves in a phantom was also evaluated: the results confirm the need to use data obtained in conditions as close as possible to the operative ones, in treatment planning as well as in studying and realizing calculation models.

Alloys↗
PubMed1990

Beta-TG and plasma catecholamines levels after sympathetic stimuli in hypertensives and patients with peripheral vascular disease.

The influence of the sympathetic nervous system on platelet functions in vivo is still controversial. The aims of our study were to compare the response to various sympathetic stimuli in normal subjects and in patients with essential hypertension (HT) or peripheral vascular disease (PVD) and to evaluate any correlations among plasma levels of catecholamines, beta-thromboglobulin (beta-TG) and platelet factor 4 (PF4). In basal conditions beta-TG and PF4 values in the HT patients were higher than those observed in the controls of the same age but lower than those of the PVD patients. Although the different sympathetic stimuli (90 degrees tilting, handgrip, treadmill test, bicycle test) caused a significant increase of the plasma epinephrine (E) and norepinephrine (NE) levels, they did not modify the beta-TG and PF4 levels in any of the groups studied. The platelet activation indices, therefore, regardless of the basal values, do not seem to be influenced by sympathetic stimulation.

Adult↗
PubMed1990

Measurements of radiocesium transfer to milk and calculation of resulting dose in Brescia, Italy, following the Chernobyl accident.

Results are presented of several measurements on components of the cows' milk chain performed at our Medical Physics Service after the Chernobyl accident. Values were obtained for Cs isotope transfer coefficients, namely, for cows' diet-milk and diet-feces transfers. Other measured parameters were the effective half-life of Cs in milk and the 134Cs:137Cs ratio. In addition, an evaluation of Cs contribution to the absorbed dose to population from milk is performed.

Accidents↗
PubMed1990

Prognostic value of hyponatremia in patients with severe chronic heart failure.

In order to evaluate the incidence and the prognostic value of hyponatremia (hypoNa) in patients (pts) with severe chronic heart failure (SCHF), the authors studied 161 consecutive pts (113M, 48F ages sixty-seven +/- ten) with SCHF in NYHA class III-IV. The cause of SCHF was ischemic in 64 pts, hypertensive in 39, valvular in 14, alcohol-related in 3, and idiopathic in 41. Pretreatment hypoNa (less than 135 mmol/L) was found in 64/161 pts (40%) (Group I); Na+ was less than 125 in 10 pts, 125-130 in 19, and 131-135 mmol/L in 35; 42/64 pts (66%) of Group I were in NYHA class IV at admission. In the pts with pretreatment Na+ less than 125 mmol/L, hypoNa was persistent and refractory to high-dose furosemide (less than 500 mg/day) and water restriction. Cardiovascular mortality of Group I pts was 69% within twenty-four months (34 pts died of low-output syndrom and 10 suddenly). All pts with Na+ less than 130 mmol/L died within six months. The 20 pts who normalized Na+ are alive, and in NYHA class II-III (follow-up: twenty-six +/- fifteen, six to sixty months). Pts without hypoNa were 97/161 (Group II), and 58/97 (60%) are alive (follow-up: thirty +/- eighteen, five to fifty-eight months), whereas 39 pts died (27 suddenly, 9 of low-output syndrome, and 3 of extracardiac disease) within twenty-four months. The mortality rate of Group II was significantly lower (40% vs 69%, p less than 0.001) compared with Group I. The two groups were similar for age, sex, and cause and duration of SCHF.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Effect of high-dose furosemide in refractory congestive heart failure.

High-dose firosemide is considered effective in primary renal sodium retention but is not generally recommended in congestive heart failure. In order to evaluate efficacy and safety of high-dose furosemide (greater than 500 mg/day), the authors studied 20 patients (pts) resistant to therapy (including furosemide less than 500 mg/day) selected from 161 pts admitted for chronic heart failure. All refractory pts (15 men and 5 women, mean age sixty +/- 12 years) were in NYHA class IV and showed hyponatremia (130 +/- 5 mEq/L) and impaired renal function (BUN 31 +/- 14 mg/dL, serum creatinine 1.3 +/- 0.3 mg/dL and BUN/creatinine ratio 23 +/- 7). In addition to digitalis, dopamine, angiotensin-converting enzyme inhibitors, or vasodilators, IV high-dose furosemide (775 +/- 419 mg/day, 500-2000) was given for ten +/- five days under daily clinical and laboratory monitoring. Three pts died of low-output syndrome while 16 pts were upgraded to NYHA class III and 1 pt to class II; a mean weight reduction of 7.3 +/- 2.9 kg in ten + five days (0.80 +/- 0.4 kg/day) and a mean diuresis increase of 88 +/- 57% occurred. The maximal dose of furosemide did not correlate with serum creatinine but did correlate with BUN/creatinine ratio (r = 0.78, p less than .001). Pts were discharged on with chronic heart failure, and 43% in the subgroup in NYHA class IV with hyponatremia. High dose furosemide was effective for rapid removal of excess water and salt in "furosemide-resistant" congestive heart failure. The relationship between renal impairment and maximal furosemide doses seems to confirm the role of renal pharmacokinetics in the appearance of furosemide resistance.

Administration, Oral↗
PubMed1990

[The recombination factor in an ionizing chamber used for dosimetry of a linear accelerator].

The authors starting from the discussion of Boag address experimentally the ion recombination in an ionizing camera. They outline the fact that several basic dosimetry protocols do not highlight the importance of the used radiation sources, beam width, ionizing camera dimensions, even though they mention to take into account the recombination factor. The authors determine experimentally the recombination factor with two kinds of ionizing camera, one cylindrical and the other flat, on a linac pulsed and scanned radiation beams. As a result it ensued that it is advisable to use a Markus type ionizing camera rather than a cylindrical one, especially when scanning beams are used, to reduce the recombination phenomena.

Models, Theoretical↗
PubMed1990

[Simulation of an instrumental head for 6 MeV electron beam therapy].

Simulation of a therapy head for 6 MeV electron beams. We present the results of a simulation, performed using a Monte Carlo method, of depth dose curves in water for electron beams of initial kinetic energy of 6.4 MeV, generated by a radiotherapy microtron MM22 Scanditronix. The Fortran code in EGS4: comparison is made between simulated curves, obtained using various approximation criteria, and the experimental one.

Electrons↗
PubMed1988

Platelet activation indices and apolipoproteins in hypertensive patients.

We have studied the platelet activation indices beta-thromboglobulin (beta-TG and platelet factor 4(PF4), triglycerides (TG), total cholesterol (TC), high-density lipoprotein (HDL), low-density lipoprotein (LDL), very-low-density lipoprotein (VLDL) and apolipoprotein (A1, A2, B, C2, C3, E) profiles of 22 untreated essential hypertensive subjects (WHO stages 1 and 2) and 22 controls, to see if there might be some causal relationship between lipoprotein abnormalities and greater platelet activation. The results showed the patients had both greater platelet activation than the controls, as demonstrated by higher plasma beta-TG levels (P less than 0.01) and lower apolipoprotein A2 levels (P less than 0.05). However there were no significant correlations between the platelet activation indices and the plasma levels of apolipoproteins, lipoproteins or lipids in either group.

Aged↗
PubMed1986

Statistical evaluation of a total dose-dose rate relationship in oral tongue cancer 192 Ir implants.

A statistical tool has been made by us on 55 patients treated for oral tongue cancer with unique 192 Ir interstitial curietherapy in Brescia from 1973 to 1981. Our aim was to verify a simple analytical relationship proposed and adopted by us for oral tongue cancer implants in order to reduce the total dose with increasing dose rates and to calculate the equivalent total dose when referred to 0.357 Gy/hr. Recurrences and radionecroses are studied in a variance analysis, distinguishing according to stage and total dose; within the dose rate range used, a highly significant difference in radionecrosis rate (P less than 0.005) confirms our isoeffect relationship.

Brachytherapy↗